Phaseolus lunatus aka Lima Bean

Phaseolus lunatus is the lima bean, also called butter bean. It belongs to the pea family, Fabaceae. Its native range runs from Mexico to Peru. It grows in tropical lands with wet and dry seasons. Wild plants grow near streams and in damp forest thickets. They also climb through shrubs along paths and fences. People grew this crop in the Americas before Europeans arrived. Today, growers raise it across tropical and warm temperate regions.

This plant can grow as an annual or herbaceous perennial. Its branched stems twine around plants or climb on supports. Without support, they spread across the ground. Stems usually reach about 13 feet [4 metres] in length. PFAF reports lengths of 20 feet [6 metres]. Useful Tropical Plants records extremes of 26 feet [8 metres]. The roots form a fibrous mass that may become fleshy. NC State records hairless leaves and stems without scent. Bees and other insects pollinate the flowers. The plant is also self-fertile.

Growers harvest both the seeds and young seedpods for food. Seed size and colour vary across the species. Some beans show lines that spread from the seed scar. Cooks use young seeds in soups and stews. They also dry mature seeds for later use. Ground dry seeds can thicken soup or supplement bread flour. People steam young pods or add them to cooked dishes. Cooked leaves provide another food source, though they can taste bitter.

Lima beans grow well in warm, lowland tropical sites. Annual rain of 900–1,500 millimetres can meet their needs. Established plants can cope with less rain. Heavy rain during flowering can reduce seed set. Heat above 30°C can also hinder fertilization. Seeds need a dry spell to mature. PFAF lists USDA hardiness zones 10–12. It advises planting seedlings outdoors after the last expected frost. The crop supplies food and fodder in mixed plantings. Growers also use it as green manure and ground cover. Its nitrogen-fixing role helps improve soil.

Raw mature seeds are poisonous and must not be eaten. PFAF and Useful Tropical Plants call for thorough cooking. NC State warns that cooking may not remove all toxins. It advises against eating ornamental striped beans. It also lists roots and seeds as highly poisonous. These sources differ on how fully cooking removes the danger. PFAF reports traditional medicinal uses for leaves and seeds. Those uses do not establish that home remedies are safe.